In recent years, requirements of photographic light-sensitive materials, particularly those for photographing have become still more severe, and photographic light-sensitive materials of high sensitivity and fine graininess have been desired.
In order to achieve fine graininess, one means wherein a photographic light-sensitive material contains emulsion grains having a high silver iodide content and controlled grain structure is proposed and described, for example, in JP-A-60-143331 and JP-A-58-181037 (corresponding to U.S. Pat. Nos. 4,668,614 and 4,477,564, respectively) (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, when this technique is applied to only one emulsion layer, the improvement in graininess is still insufficient. Further, there is a problem in that silver salt and/or silver are difficult to remove in a desilvering step, particularly in a fixing step as the silver iodide content increases as described in JP-A-62-7041.
It is also described that a photographic light-sensitive material in which the average silver iodide content of silver halide in all silver halide emulsion layers is not less than 8 mol% provides improved graininess in JP-A-60-128443. However, that silver iodide content is still insufficient to improve graininess. In addition, there are problems in the material's resistivity to irradiation of radioactive rays and its desilvering property.
On the other hand, photographic light-sensitive materials containing the compound according to the present invention are described, for example, in JP-A-62-89952 and JP-A-61-282841 (corresponding to GB-A-2,176,304 and U.S. Pat. No. 4,849,324, respectively). However, it has been believed that such a compound is preferably employed in combination with a silver halide emulsion having a low silver iodide content in view of its photographic properties such as sensitivity or fog and processing aptitude as described in the above patents.
However, it has become apparent to the applicants that an increase in fog, a decrease in sensitivity and degradation of graininess are very serious when a light-sensitive material containing an emulsion having a low silver iodide content is exposed to natural or artificial radioactive rays. Further, the desilvering property thereof is not good. It has been hitherto believed that a low silver iodide content is indispensable for shortening the desilvering step as described in JP-A-62-89963 (corresponding to U.S. Pat. No. 4,745,048).